The invention relates to reducing noise from a gear wheel by coupling a vibration damping mass to the gear wheel.
DE 43 31 165 A1 describes a chain drive mechanism of this generic type having a chain wheel, on either side of which an elastic rubber disc is secured in order to reduce noise. The rubber discs are attached to the chain wheel by means of adhesive or by sintering. This known solution is not suitable for a gear wheel used in a gear system subjected to high load and in constant contact with hot gear oil. On the contrary, it would pose the greatest possible risk of failure in such a gear system since it would be impossible to guarantee that the rubber discs would not come unstuck, at least partially.
DE 39 07 153 describes a pair of gear wheels, the teeth of which are provided with an annular disc on opposing sides in the region of their ring gear in order to damp the noise caused by the meshing of their teeth. The point at which the noise arises is therefore relatively well encapsulated by the annular discs so that the directly generated sound can not be transmitted further. However, this advantage comes at a price since more space is required for the gear wheels at the side. Furthermore, the vibrations resulting as the teeth mesh are largely unaffected as they are transmitted as a structure-borne sound across the entire body of the gear wheels. Consequently, depending on how the annular disc is attached, the noise transmitted across the side faces of the gear wheels is damped to a greater or lesser degree and noise-damping of the gear wheels as a whole is not satisfactory.
The objective of the invention is to provide an anti-noise gear wheel which is simple to construct and whose vibration-damping mass can be mounted in the gear system using standard means.
The features by which this objective is achieved are set out in the characterising part of the main claim. By an appropriate selection of the material used for the vibration damping mass, the specific weight of which should not differ too greatly from the specific weight of metals, full surface application on the gear wheel can be achieved by appropriate means without any specific complexity. As a result, the vibration behaviour of the gear wheel is effectively damped in such a way that it is no longer necessary, as has been the case to date, to use adhesive to couple the vibration damping mass firmly with the gear wheel. Bonding methods are not practical for use in gear assembly lines and automatically mean that separate working sections have to be provided in the areas where the gear system is assembled or elsewhere, so that appropriate steps can be taken to protect personnel from the toxic vapours generated when using adhesive.
In one practical embodiment of the invention, which affords the highest degree of noise damping, the vibration damping mass is designed as an annular disc which covers a predominant proportion of the side face of the gear wheel almost as far as the ring gear.
In order to take the load off the means for applying the annular disc against the gear wheel, the gear wheel is provided with a hub on which the annular disc is retained.
By virtue of one advantageous embodiment of the invention in which a single element only is needed in order to apply the annular disc, the annular disc is applied under the force of an element arranged on the hub, pre-tensioned to a defined degree against the side face of the gear wheel, the element being a shaft-retaining ring.
Another embodiment of the invention is characterised by the fact that the annular disc is applied against the side face under the force of a ring pressed onto the hub.
Another embodiment of the invention is characterised in that the annular disc is coupled with the gear wheel by means of screws and/or rivets.
In order to secure efficient noise damping even in applications in which the gear wheel is susceptible to rotary vibrations originating in the drive, the invention proposes another feature whereby the annular disc is prevented from rotating relative to the gear wheel by means of a rotary locking mechanism.
A first solution to securing the annular disc consists in using a clamping sleeve to prevent the annular disc from rotating.
A second solution to securing the annular disc is to prevent the annular disc from rotating by embedding an element with a high friction value (O ring) in the end face.
In order to keep the space requirement to the sides of the gear wheel to a minimum, the invention proposes another feature whereby the annular disc is mounted in a recess of the gear wheel.
A not inconsiderable improvement to noise damping can be achieved if the vibration damping mass is provided in the form of at least two annular discs arranged one directly on top of the other and the vibration damping mass is made from a material with an E-modulus comparable with that of the material of the gear wheel.